The invention relates to the cooling of the electrical and/or electronic control and monitoring circuits of an air-conditioning system.
It relates more particularly to a compressor, especially for a system for air-conditioning the passenger compartment of a motor vehicle, comprising a casing defining a high-pressure chamber enclosing a system for compressing a refrigerant fluid which circulates in the air-conditioning system, this compression system taking in the refrigerant fluid at low pressure and delivering it at high pressure into the high-pressure chamber, an electric motor for driving the compression system and electronic means for control and monitoring of the operation of the electric motor.
The compressors used to compress a refrigerant fluid in a system for air-conditioning the passenger compartment of an electrified motor vehicle are controlled by power electronics circuits. The speed of rotation of the compressor is controlled by an inverter which gives rise to thermal losses during its operation. This is why it is necessary to cool these electronic circuits in order to ensure their operation and to extend their lifetime.
A compressor of the hermetically sealed type is already known (U.S. Pat. No. 6,041,609 DANFOSS) in which the inverter governing the rotational speed of the compressor is housed in a box fixed to the outside of the casing of the compressor, and is cooled by contact and heat exchange with the intake tube before the refrigerant fluid coming from the evaporator enters the compressor.
A compressor of this type exhibits several drawbacks. It is of substantial size because of the presence, on the outside of the compressor, of a box in which the electronic components are housed. It is relatively complex to manufacture and to assemble because it is necessary to provide a modification to the intake line so that it provides the necessary and sufficient surface area for contact and heat exchange.
The subject of the present invention is precisely a compressor of the type defined in the introduction, which remedies these drawbacks.
This compressor includes a low-pressure intake chamber for the refrigerant fluid integrated in the casing, which is separated from the high-pressure chamber by a separating partition, the electronic means for control and monitoring of the operation of the electric motor, which are placed in the intake chamber, being cooled by the refrigerant fluid.
By virtue of these characteristics, a compressor featuring great compactness is produced. This compressor can easily be mounted into the vehicle, because there is a single component to be fixed, and a single area for connecting the electrical and electronic circuits. The sound level of the pulsation of the gas on the intake line of the compressor, as well as the mechanical noises given off by the compression pump and its valve are reduced by the presence of a buffer volume consisting of the intake chamber.
The cost of manufacture of this compressor is reduced by the integration of the electronic circuits for control of the motor of the compressor in a single casing.
Finally, the losses by Joule effect in the phase wires linking the inverter to the motor are reduced to practically nil as a result of the short length of these connections.
The compressor preferably includes a separate chamber for electrical connection of the motor, defined in the casing, this separate chamber communicating with the high-pressure chamber via a passage.
The intake chamber and the separate chamber for electrical connection of the motor are advantageously presented as cavities which are open towards the outside of the casing and are closed off by a cover plate which is common to the two chambers.
In one preferred embodiment, the cover plate is a terminal plate equipped with all the connecting terminals necessary for the operation of the compressor. The input and output terminals for the power supply to the electric motor and outlet terminals for motor information (for example on the temperature of the motor) are situated in a part of the terminal plate which closes off the separate chamber for connection of the electric motor, and the other connecting terminals are situated in a part of the terminal plate which closes off the intake chamber.
Advantageously, the outlet terminals from the intake chamber and the input terminals of the motor in the separate chamber are fixed, permanent and insulated as from delivery of the terminal plate before it is mounted onto the casing of the compressor.
According to another characteristic of the invention, the electronic means for control and monitoring of the operation of the compressor are arranged on a power module including a metal cooling sole plate.
According to another advantageous characteristic of the invention, the electronic means for control and monitoring of the operation of the compressor are connected to the power module, and these electronic means and the power module, with the exception of the cooling sole plate, are coated in an overmoulding of plastic.
This plastic must be compatible with the refrigerant fluid and the lubricating oil of the compressor. It is preferably chosen from the family of elastomer polyester thermoplastics. It is preferred to use an elastomer polyester plastic known by the commercial trademark HY-TREL G 3548 from the Dupont Company of Nemours.
In one preferred embodiment, the casing is produced as a first part containing the gas-compression system, the intake chamber and the separate electrical-connection chamber, and a second part containing the electric motor, these two parts being assembled to one another along a junction plane.